Some TV shows win you over with casting, some with plots and others with dialogue.

Call the Midwife, the new British period drama that began its run on PBS’ Masterpiece on Sept. 30, had me at “I got some shocking discharge.”

This was not a reference to someone leaving the military. Rather, it was a line uttered by a slatternly pregnant woman who was lying on a medical examination table in London as a fledgling midwife was about to peer between her legs. The look of disgust on the midwife’s face couldn’t have been more eloquent.

Clearly, we’re a long way from Downton Abbey and its genteel divertissements. Then again, how many fans of that Masterpiece series were first won over in season one when a young, handsome Turkish diplomat unexpectedly expired in Lady Mary’s bed?

Scenes like these are why we love it when period British dramas come calling on Masterpiece. The standard reasoning is that if it’s British, it must be good. The characters are wearing old-timey costumes, so it’s history and we’ll learn something. Or it’s based on a famous novel, so it’s educational. But the dirty little secret to the appeal of these shows, and it goes back all the way to such early progenitors as The Forsyte Saga (the 1967 original, not the 2002 remake) and Upstairs, Downstairs (also the original), is that there’s going to be romance and discreet sex and, best of all, yearning glances.

Call the Midwife, which first aired to sizable ratings on England’s BBC network earlier this year, is set in the slums of London’s East End in 1957. Based on a trilogy of memoirs by the late Jennifer Worth, Midwife tells the story of Jenny Lee, a newly graduated nurse and midwife, who leaves her protected middle-class home to live and work alongside other nurses and medically trained nuns at Nonnatus House. (The character is played by Jessica Raine; Vanessa Redgrave chimes in with voiceovers as an older version of Jenny reminiscing about her past.)

Their patients are women with too many children and too little money who live in overcrowded apartments, sometimes with a husband and sometimes not. These women, as our heroine comes to realize, are fantastically brave, carrying on and enduring in the face of overwhelming odds, not the least of which is England’s rigid class system, which was only beginning to loosen up during that period.

The series offers the usual attractions of any medical drama: life and death stories and a revolving carousel of patients, with new ones hopping on and off every week, which keeps things fresh. There’s the Spanish immigrant who has 23 children and is about to have her 24th; a young woman who at 23 is already having her fourth child; and the aforementioned unfortunate woman with the discharge, who turns out to be suffering from syphilis.

The show also provides a revealing look at the early days of England’s vaunted National Health Service, the government-sponsored, single-payer health care system that Americans, depending on one’s political views, either envy or despise.

In the first episode, a woman gives birth to a preemie at home. A doctor who arrives to help to save both her and the baby credits the National Health Service. “Ten years ago we’d have had none of this, no obstetrical flying squad, no ambulance and no chance,” he says.

Midwife is a nostalgic reminder of how medicine used to be practiced. In an era of institutional medicine, crammed waiting rooms, anonymous specialists and insurance bureaucracy, these nurses and midwives mount their bicycles to visit patients in their homes, sometimes daily. They take the time to share a meal or have a cup of tea with a patient and their family. They toil night and day, always answering the phone then jumping on their bikes to ride through soupy fog to get to a patient in need.

When was the last time you had that kind of response from a nurse or doctor? At my G.P.’s office, no one even answers the phone during lunchtime. Callers are brusquely informed via a recording to call back later.